How safe is the water that we swim in?

Swimming is a well- rounded, injury free sport, with a whole range of health benefits. It is also considered to be extremely safe. But how safe really is the water that we swim in

I’m a regular swimmer at The College pool and really enjoy making good use of this facility. I’ve always thought of swimming pools as clean and never really focused (until just recently) on the chemistry that goes on in the pool itself. This chemistry, however, is what determines the safety of the pool.

In the early twentieth century, the only process of dirt removal was via filtering. A study in 1910 by public health officials showed that more than 111,000 microbes were present in every cubic centimetre of water samples from local swimming pools. This meant that public pools at that time could have been compared to dilute sewage - it’s not surprising that so many more people caught diseases and illness! Thankfully we have moved on and there are currently multiple methods of disinfection. While water is still filtered constantly throughout use, public pools make use of chemical disinfection to keep harmful bacteria to a minimum. However, there are harmful side-effects associated with these chemicals disinfects that we swim alongside.

Most pools nowadays use chlorine. Chlorine is a powerful oxidant (oxidation damages and kills cells) and so can remove bacteria and viruses with speed. Chlorine’s efficiency at removing bacteria makes it one of the best disinfectants.

However, pure chlorine is too dangerous to use alone and is instead implemented through solid salts of tablets which contain chemicals like sodium hypochlorite (NaOCl) or calcium hypochlorite. These react with water to produce the bacteria-killing hypochlorous acid (HClO). However, even the use of these “safe” tablets can cause harm through triggering disinfection by-products, known as DBPs.

Some of the more common dangerous by-products (DBPs) include chemicals like trihalomethanes and chloramines, which form at the surface of the pool and can cause or irritate asthma symptoms. In a recent Norwegian study of 313 swimmers, of whom 22% overall had asthma, rates increased to 36% for the swimmers

who spent 16 plus hours weekly in the pool.

Marlborough College Swimming Pool

The swimming pool at Marlborough College doesn’t focus on chlorine, and instead primarily uses ultraviolet (UV) light to disinfect the pool, giving excellent water quality in which there is a much lower chance of DBPs being formed due to the lower levels of chlorine.

What Can We do to Keep the Pool Clean?

Showering is key. Although many people disregard it, showering can wash off the bodily secretions and skin products (e.g., sunscreen and sweat) on our skin that can mix with the disinfection chemicals to produce the harmful by-products. Having a well-ventilated pool also makes a big difference and should be a consideration for any serious swimmer that uses a traditional chlorinated pool.

Do not let this stop you from swimming. We should simply aim to maintain pools to facilitate for healthy swimming to continue. Keep on swimming!

By Harry W (Re)